Additive Manufacturing of Graphene Nanoplatelets and Hexagonal Boron Nitride Composites via Stereolithography

Abstract

The ability to utilise graphene and related 2D materials within additive manufacturing sparks a promising future for developing multi-functional composites on a commercial scale. 2D materials can be exfoliated into platelets with high aspect ratios and re-dispersed within a polymer resin to produce inks suitable for 3D printing. Such inks can be combined with a photoinitiator to form photocurable inks for the use in stereolithography. This work presents the manufacture of 3D printed boron nitride (BN) and graphene nano-platelets (GNP) composites with enhanced thermal conductivities for potential uses in thermal management applications. Key manufacturing parameters, such as the critical exposure and depth of penetration from the SLA laser are investigated to facilitate formulation and printing of 3D structures. The scattering effects of the 2D materials are explored using semi-empirical models to understand why the maximum printable solid loadings of the inks are 20 wt. % and 4 wt. % for BN and GNP respectively. The intrinsically high thermal properties of GNP (3000 W.m-1.K-1) (XG Sciences) and BN (400 W.m-1.K-1) can be applied for thermal management in electronics to produce efficient systems with increased operating times eliminating short-circuiting from occurring. An increase in thermal conductivity of over 233 % has been observed with the addition of 20 wt. % BN (0.70 W.m-1.K-1) and 200 % for 4 wt. % GNP (0.55 W.m-1.K-1) when compared to the UV polymer (0.21 W.m-1.K-1). An increase in mechanical properties of the polymer matrix has also been observed with BN and GNP platelets acting as reinforcements. GNP and BN can be coupled to form hybrids with synergetic capabilities for improved thermal and mechanical properties of polymers. The electrically insulating hexagonal BN platelets have been dispersed with GNP platelets to form photo-curable hybrid inks for SLA. The hybrids showed a maximum thermal enhancement of 238 % Hybrid 1 (0.71 W.m-1.K-1) compared to UV polymer (0.21 W.m-1.K-1) and an electrical resistivity of 1.81 x1010 Ω.m. Heat sinks containing hybrid materials were 3D printed and tested for potential applications in thermal management of electronic devices by measuring the heat transfer through the printed structure over time. The hybrid heat sinks reached the set temperature 43 % faster than the control displaying improved heat transfer and heat dissipation required for heat sink applications.

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Brian Derby (Supervisor) & Suelen Barg (Supervisor)